Project Summary Congenital birth defects affect more than 7 million births annually worldwide and one third are associated with craniofacial abnormalities that often result in severe deformities. One of the most extreme craniofacial disorders is Treacher Collins Syndrome (TCS), characterized by an underdeveloped lower jaw and cheek bones. The most severe TCS cases result in infant death or significant lifelong morbidity due to an array of symptoms that include loss of hearing and vision, problems with eating and breathing, and delayed brain development. There are no known cures for TCS, and symptoms can only be managed postnatal by a comprehensive multi-stage surgical reconstruction from infancy to adulthood. Because TCS treatments are seldom fully corrective and are exceedingly expensive, there is a clear need to develop prenatal therapeutic approaches to ameliorate and possibly prevent TCS. If we plan to develop novel strategies to prevent TCS, then it is essential that we understand TCS at its most basic molecular level. The long-term objective of this research proposal is to build a solid foundation of preliminary studies to develop an R01 proposal focused on elucidating the molecular mechanism of how TCS-associated mutations disrupt the Pol I transcription process. The rationale is that elucidating the molecular mechanism of TCS mutations will help us better understand the connection between dysregulated Pol I and TCS. We hypothesize that TCS-mutations disrupt essential molecular interactions within the Pol I interaction network that results in ribosome deficiency and disease. To test this, we propose the following two specific aims:1) Identify genetic suppressors of the TCS phenotype in yeast that will guide future studies of these potential suppressors in more complicated disease models, and 2) Determine how TCS mutations disrupt Pol I complex integrity in various cell types that will guide future studies on appropriate disease models. To accomplish these aims, we will use an interdisciplinary combination of well-established and complementary molecular genetic, biochemical, and biophysical approaches to systematically characterize and suppress TCS mutant phenotypes. The proposed research is significant because it will lead to a detailed understanding of the molecular basis of TCS mutations that has the potential to alter current molecular paradigms for the regulation of rRNA synthesis in facial bone development and may illuminate new starting points for preventative therapies.